1. Field of the Invention
This invention relates to celulose packaging material particularly adapted for packaging soft cheeses. More specifically, the subject invention relates to a cellulose film packaging material especially useful for packaging soft cheeses which have not yet fully ripened and to a process for preparing the cellulose film packaging material.
2. Discussion of the Prior Art
Soft cheeses such as Camembert, Coulommier, Brie etc., are packaged in suitable packaging material before the cheese has completely ripened. After packaging the ripening process will continue until the cheese is consumed. This can often occur as much as a month or more after packaging. Basically, the ripening process is a dynamic bacterial fermentation process during which the cheese absorbs oxygen from the atmosphere and releases carbon dioxide. It is therefore necessary that the packaging film for soft cheeses should be sufficiently permeable to oxygen and carbon dioxide to allow the ripening process to proceed smoothly and under conditions such that the cheese will be sufficiently ripened for the particular type of cheese.
Moreover, soft cheeses are characterized by having a rather high moisture content. It is therefore essential that the packaging material not only be permeable to oxygen and carbon dioxide but also be permeable to the passage of water vapor contained within the cheese product. However, while the packaging material must be sufficiently permeable to water vapor to avoid condensation of water on the surface of the cheese which would result in destruction of the bacterial molds, the permeability to water vapor must not be sufficiently high such that the cheese will dry out during the ripening process.
The various factors which effect the development of a ripened soft cheese include, for example, the initial composition of the cheese culture, e.g. quality of the milk, bacterial culture, and the like; climatic conditions during the manufacturing process; ripening conditions, e.g. temperature, humidity, etc; storage conditions; gas exchange with the ambient environment, after packaging, with, in particular, water vapor, oxygen, carbon dioxide and ammonia; and heat exchange with the ambient environment.
As noted above the packaging material for packaging soft cheeses must not be impermeable to water vapor since it would otherwise promote proteolysis which will accelerate the degradation of the bacteria resulting in an unusable product. Furthermore, if water is permitted to condense on the surface of the cheese it would promote conditions which are unfavorable to the existence of the microbial flora which imparts to the cheese its characteristic flavor and texture.
On the other hand, if the packaging material is too permeable to water vapor it will permit the surface of the cheese to dry out. This in turn results in a correlative increase in the salt content, weight loss, incomplete ripening and the appearance of pock marks or indentations on the cheese which render the cheese unacceptable to the consumer. It is therefore apparent that the gas and vapor permeability of packaging materials for soft cheeses must be carefully selected to take into account each of these factors so that a finished product of high quality can be consistently obtained. The packaging material must be sufficiently permeable to oxygen to promote the development of the surface microbial flora (e.g. Penicillium caseicolum) and also sufficiently permeable to the carbon dioxide and ammonia generated which inhibit the development of the surface flora.
The materials most commonly used for packaging soft cheeses are waxed paper, perforated cellulose film, or multi-layered laminates such as cellulose films/waxed paper, super coated paper/wax paper, aluminum/glassine paper/waxed paper. The double paper laminates are generally considered the most economical but the cellulose film/waxed paper laminates generally give better results with respect to the conservation, refining and appearance of the packaged product. The waxed paper is placed in contact with the cheese and permits absorption of a part of the water from the cheese and desorption through the outside cellulose film to thereby avoid surface condensation which is harmful to the Penicillium.
Uncoated cellulose film or cellulose film coated with a nitrocellulose film are sufficiently permeable to oxygen and carbon dioxide to permit ripening of soft cheeses. It is generally considered that only the nitrocellulose varnish films are sufficiently permeable to water vapor to be usable in packaging soft cheeses and therefore nitrocellulose coated films are considered to be particularly useful for this purpose. However, the commercially available nitrocellulose coated films are generally characterized by too high a water permeability. To overcome this problem it has been suggested to incorporate paraffin or other water-proofing agent into the nitrocellulose coating in an amount sufficient to lower the water vapor permeability to a degree which depends on the particular cheese.
However, while the paraffin containing nitrocellulose coatings have met with some commercial success because of their simplicity of manufacture and their low cost they are not totally satisfactory with respect to their water vapor permeability to improve the water vapor permeability, it is necessary to perforate the paraffin containing nitrocullulose water film. However, the water vapor permeability has not been uniform over the entire surface of the film and accordingly these films have been characterized by the appearance of mold rot at various random points on the surface or crust of the cheese due to the condensation of water vapor at these points.
Accordingly, it is an object of the present invention to provide a cellulose packaging film for moisture containing food products, particularly cheeses and especially soft cheeses which avoids these drawbacks and yet which is simple to prepare, economical, and comprised only of ingredients which are generally recognized as safe as packaging materials for food stuffs.